In the second programme in the series, Wild Underground, biologist, Mike Dilger ventures underground once again, but this time he explores how animals are adapted to survive and thrive in the complete darkness of the subterranean world of caves.

The programme begins with Mike abseiling from a rocky ledge, down into a deep hole, following the course of a waterfall, which has carved out a deep underground cavern in the Yorkshire Dales. By abseiling into the cave, Mike gains an insight into how animals can find their way into these underground environments and how caves can provide a wonderful escape from predators above ground.

Here, in the Yorkshire Dales, many of the caves are used by five species of bats which roost here at night safe from predators. In addition, its believed that bats gather to mate at the entrance to these caves, as Mike discovers, when at the end of the programme, he joins John Altringham and a group of his PhD students from Leeds University to discover how a dusting of fluorescent LOVE DUST is helping scientists understand the bats arduous behaviour!!

John also joins Mike on his cave expedition as does Anita Green (Ph.D. student) and Graham Proudlove, biological recorder with the British Cave Research Association, and a specialist on cave fish.

The expedition through the cave proves to be both fascinating and challenging for the group. The caves are wonderfully evocative as the sounds of dripping water and pounding waterfalls echo through the tunnels and accompany our intrepid adventurers. Much of the expedition involves scrambling on their hands and knees, or wading through icy rivers of water, or scrambling and sliding on their stomachs through the “Squeeze”, an incredibly narrow twisting corridor of rock, and ather smaller than Mike!

The expedition through the cave though, is more than just a “Boy’s Own” Adventure story : it highlights the harshness of these environments and illustrates how animals which do live down here are very well adapted : bats for example use echolocation (a system of shouting and listening to echoes to gain a 3-D image of their world), to navigate their way through the dark twisting passages. Over generations, fish in caves lose their pigments and their eyes but develop enlarged lateral lines which help them balance and negotiate their passage. Many insects evolve longer legs and antennae to help find their way through the dark.

The programme inter-cuts Mike’s experiences, with insights into life in tropical caves where owing to the lack of ice during glaciation, there is a much greater diversity of wildlife. In some areas, crocodiles can be found slipping quietly through the dark waters: whilst in others, the caves echo with the screeches of millions of bats: and there are also tales of encounters with wasp nests blind fish and clicking birds!